The present invention relates to an electrophotographic printer, such as an optical printer or digital printer having a carrier generation layer and an overcoat layer thereover. More particularly, the printer utilizes a function-separating type photoconductor in which the carrier generation layer has high sensitivity and high plate wear resistance.
During operation of the printer several steps are repeated in sequence, i.e., electrification of the photoconductor, exposure to light to form an image pattern in the electrified photoconductor, development of the image using toner, transfer of the toner particles to paper, and removal of residual electric charge.
The photoconductor conventionally used in an optical printer, digital copier or the like, consists of a multilayer film comprising an overcoat layer of Se-As alloy containing relatively low percentages of arsenic. A photoconductor of this type can, on the average, produce only one hundred thousand printed sheets or less before the image quality begins to deteriorate. One of the present inventors has developed a photoconductor whose overcoat layer consists of As.sub.2-x Se.sub.3+x, where 0.ltoreq.x.ltoreq.0.5. This photoconductor has improved physical properties, especially improved hardness, and thus exhibits greatly improved plate wear resistance. An overcoat layer of this type has been described in commonly owned U.S. patent application Ser. Nos. 192,470 and 192,471, both filed May 10, 1988, incorporated herein by reference.
Unfortunately, the provision of the overcoat layer having the composition given by As lowers the surface potential and produces clouded images when used in conventional printers. Further, the potential contrast decreases, deteriorating the gradation and impairing the print quality.
It is thus an object of the present invention to provide a printer employing a function-separating type photoconductor having an As.sub.2-x Se.sub.3+x overcoat layer which is free of the foregoing difficulties.
It is a further object to provide such a printer which suppresses decrease in the potential created by electrification.